Industrial Robot Arm Kinematics for Constant Tilt and Large Workspace
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Solution Overview
Problem
Existing robot arm designs face challenges in achieving a lightweight, high-speed, and safe structure with a large workspace, as they either require substantial space or compromise on workspace size due to limitations in kinematic chain configurations and added weight from wrists and cabling.
Innovation Solution
A robot arm design featuring a first, second, and third actuator configured to rotate an inner arm-assemblage, outer arm-linkage, and end-effector platform around distinct axes, utilizing a slim kinematic chain structure with parallel links and bearings to maintain constant tilt angles without additional wrist motions, allowing for six degrees of freedom with all actuators fixed to the stand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a parallel kinematic robot structure is used to achieve light weight, then the robot arm weight is reduced, but the workspace becomes very small in relation to the space needed for the arm system
Solution Approach 1:
The patent transitions from traditional parallel kinematic structures requiring large horizontal space to a vertical configuration where the robot arm system extends primarily in the vertical dimension. The arm system can reach heights of several meters while occupying minimal floor space, effectively trading horizontal area for vertical volume to resolve the space contradiction.
Solution Approach 2:
The patent employs a nested configuration where multiple kinematic chains and arm linkages are arranged concentrically and vertically stacked. The inner and outer arm linkages are positioned one within another, allowing the robot to achieve extended workspace while keeping the overall footprint compact, thus reducing the space needed for the arm system.
2Manufacturing precision
If a two DOF wrist is added to maintain constant tilt angle, then the end-effector positioning accuracy is improved, but the robot arm weight increases substantially
Solution Approach 1:
The patent extracts the constant tilt angle maintenance function from a separate wrist mechanism and integrates it directly into the kinematic chains connecting the actuators to the end-effector. By embedding the tilt control within the existing arm linkages and joints, the system achieves positioning accuracy without adding the substantial weight of a dedicated two DOF wrist assembly.
Solution Approach 2:
The patent designs the kinematic chains to serve multiple functions simultaneously: they provide both the primary positioning movements and the constant tilt angle maintenance. The same links and joints that enable end-effector movement also constrain the tilt angle, eliminating the need for separate wrist actuators and reducing overall system weight while maintaining positioning accuracy.
3Adaptability or versatility
If three separate kinematic chains are used to connect actuators with end-effector, then the robot can achieve six degrees of freedom, but the space needed for the arm system becomes very large
Solution Approach 1:
The patent arranges three kinematic chains in a nested configuration where inner chains are positioned within outer chains, and linkages are stacked vertically. This concentric arrangement allows all six degrees of freedom to be achieved while the arm system occupies minimal horizontal space, as the chains are layered rather than spread out laterally.
Solution Approach 2:
The patent configures the three kinematic chains to operate primarily in the vertical dimension rather than spreading horizontally. By stacking the chains and arranging joints vertically, the system achieves full six-degree-of-freedom capability while confining the arm system to a compact footprint, effectively using vertical space to reduce horizontal area requirements.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3D
AI summary
A robot arm (500) for end-effector motion. The robot arm comprises a first actuator (4) and a first kinematic chain from the first actuator to an end-effector platform, which gives a first degree of freedom for positioning the end-effector platform. The robot arm also comprises a second actuator (5; 5b) and a second kinematic chain from the second actuator to the end-effector platform, which gives a second degree of freedom for positioning the end-effector platform. The robot arm further comprises a third actuator (6; 6b, 512) and a third kinematic chain from the third actuator (6; 6b) to the end-effector platform, which gives a third degree of freedom for positioning the end-effector platform. The robot arm also comprises a fourth actuator (50; 150) and a fourth kinematic chain configured to transmit a movement of the fourth actuator to a corresponding orientation axis (65) for an end-effector (28). The fourth kinematic chain comprises an orientation linkage (52, 57, 59; 202, 204, 207, 209; 284, 286; 251, 256, 258) mounted to the inner arm-assemblage via at least one bearing (53, 55; 206), and an orientation transmission (64B, 64A, 216; 64C, 64D, 64E; 100, 64A; 281, 279, 275; 260, 262, 264, 266, 271, 270) mounted to the end-effector platform, wherein the orientation linkage comprises an end-effector rotation link (59; 209; 258; 281) and joints (58, 60; 208, 210; 257, 259; 257, 259; 282, 280) that provide at least two degrees of freedom for each end joint of the end-effector rotation link.